This application is based on the applications Nos. 2000-53985 and 2000-116494 filed in Japan, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a three-dimensional object printing apparatus and method for printing (image recording) on a three-dimensional printing object (three-dimensional object).
2. Description of the Background Art
Previously known printing apparatuses print a desired image and the like by ejecting ink on printing paper using an ink jet technique or the like. In such printing apparatuses, an ejection head ejects ink while continuously moving in a main scanning direction. Upon completion of a single line of printing in the main scanning direction, the ejection head is moved a fixed distance in a sub-scanning direction orthogonal to the main scanning direction and then starts the next printing operation in the main scanning direction. To improve the efficiency of such printing operations, the ejection head may be a multinozzle head with a plurality of ejection nozzles.
With the technique of ejecting ink from such a multinozzle ejection head by using the ink jet technique or the like, an attempt is now being made to perform printing on a three-dimensional printing object.
In the manufacture of the ejection head with a plurality of ejection nozzles, however, variations occur in the machining accuracy of the ejection nozzles. Further, water-repellent treatment, which is applied to around nozzle bores of the respective ejection nozzles for the prevention of adhesion of ink droplets, may be nonuniform.
Because of those factors, when the ejection head with a plurality of ejection nozzles ejects ink, the angles (directions) of ink ejection can vary from ejection nozzle to ejection nozzle.
FIGS. 32A and 32B show the directions of ink ejection from an ejection nozzle. FIG. 32A illustrates ink ejection from an ejection nozzle with high machining accuracy and uniform water repellency, and FIG. 32B illustrates ink ejection from an ejection nozzle with low machining accuracy or nonuniform water repellency.
From an ejection nozzle 152 with high machining accuracy and uniform water repellency as shown in FIG. 32A, ink is ejected in the direction of the normal to the ejection nozzle 152 and an ink droplet strikes precisely at a position PA on a printing object where a dot is to be formed.
From an ejection nozzle 152 with low machining accuracy or nonuniform water repellency as shown in FIG. 32B, on the other hand, ink is ejected in a direction that deviates from the direction of the normal to the ejection nozzle 152 and an ink droplet strikes not at the position PA on a printing object where a dot is to be formed but at a position PB responsive to the deviation in the direction of ink ejection. In this case, a striking position error h occurs between the desired dot forming position PA and the actual dot forming position PB, which reduces the precision of printing.
Generally in the manufacture of multinozzle ejection heads, it is difficult to manufacture all ejection nozzles with a high degree of precision and uniform water repellency as shown in FIG. 32A. Instead, many ejection nozzles produce a fixed error in the direction of ink ejection as shown in FIG. 32B. The problem here is thus how to reduce the striking position error h as above described.
Further, since the ejection head continuously moves in the main scanning direction during a printing operation, nonuniform speeds of ink ejection from the respective ejection nozzles also cause variations in the direction of ink ejection therefrom. This produces the striking position error h as above described, resulting in degradation in image quality.
In printing on a planar object such as printing paper, the striking position error h can be reduced by adequately reducing a distance H between each ejection nozzle and the printing object.
In ink ejection on a three-dimensional printing object, on the other hand, the distance H between each ejection nozzle and the printing object cannot be reduced adequately enough to avoid interference therebetween, depending on the shape of the printing object. Further, the distances H between the ejection nozzles and the printing object vary according to the shape of the three-dimensional surface: the greater the distance H, the larger the striking position error h. This further reduces print quality.
Therefore, it is desired to use a multinozzle ejection head for doing printing on a three-dimensional printing object without image degradation.
There also have been previously known three-dimensional object printing apparatuses for printing on surfaces having three-dimensional geometry. For example, the technique disclosed in Japanese Patent Application Laid-Open No. 5-318715(1993) provides a mechanism for supporting an ink-jet printhead to be vertically movable and adjusting the angle of inclination of a printhead arm, thereby doing printing (coloring) by means of ink ejection from the ink-jet printhead with a predetermined spacing between a printing surface of a three-dimensional printing object and the ink-jet printhead. Such a construction permits surface printing on printing objects which include not only bodies of revolution such as spheres and cones but also different-diameter bodies of revolution such as barrel bodies.
Now, it is desired that the three-dimensional object printing apparatuses can do printing on objects having more common three-dimensional geometry, but in that case it is expected that control of the inclination, the scan path, and the like of the ink-jet printhead will become complicated. Consequently, high-speed printing becomes difficult.
Therefore, it is also desired to facilitate control of the inclination and position of the ink-jet printhead relative to the surface of a three-dimensional object, thereby achieving a high-speed printing operation.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
The present invention is directed to an apparatus for supplying ink to the surface of a three-dimensional object.
According to an aspect of the present invention, the apparatus comprises: a holding section for holding the three-dimensional object in any desired attitude with respect to three axial directions; an ejection section for ejecting ink; a mechanism for positioning the ejection section in any desired three-dimensional position while maintaining the attitude thereof with respect to the three-dimensional object which is held by the holding section; and a controller for controlling the mechanism such that the ejection section performs two-dimensional scanning of a predetermined area of the three-dimensional object which is held in a certain attitude.
This apparatus facilitates control of the inclination and position of the ejection section relative to the surface of the three-dimensional object, thereby achieving a high-speed printing operation.
According to another aspect of the present invention, the apparatus comprises: an ejection section for ejecting ink; a mechanism for changing relative positions and relative attitudes of the ejection section and the three-dimensional object; a processing section for approximating a predetermined area of the surface of the three-dimensional object by a flat face; and a controller for controlling the mechanism to change the relative positions of the ejection section and the three-dimensional object while maintaining the relative attitudes thereof in a plane parallel to the flat face.
As compared with the apparatuses for printing an image in accordance with the shape of the three-dimensional object, this apparatus facilitates control of the inclination and position of the ejection section relative to the surface of the three-dimensional object, thereby permitting high-speed printing.
According to still another aspect of the present invention, the apparatus comprises: an ejection head with a plurality of nozzles for ejecting ink to the surface of the three-dimensional object located opposite the nozzles; a scanning section for causing the ejection head to scan the surface of the three-dimensional object; and a controller for enabling predetermined nozzles and disabling the other nozzles out of the plurality of nozzles in accordance with a shape of the surface of the three-dimensional object located opposite the ejection head, thereby to control scanning by the scanning section and ink ejection by the ejection head.
This apparatus permits proper printing on a three-dimensional printing object without image degradation.
According to still another aspect of the present invention, the apparatus comprises: a table to place the three-dimensional object, the table being rotatable about an axis perpendicular to a placing surface of the table; an ejection head with a plurality of nozzles for ejecting ink, the ejection head being capable of being positioned in any desired position in three-dimensional space; and a controller for controlling ink ejection from the ejection head in response to rotation of the table, by rotating the table with the ejection head in a predetermined position in three-dimensional space so that ink is supplied to the three-dimensional object with a predetermined width in a direction of the axis.
This apparatus permits proper and high-speed printing on a three-dimensional printing object without image degradation.
The present invention is also directed to a method of supplying ink to the surface of a three-dimensional object.
According to an aspect of the present invention, the method comprises the steps of: a) approximating a portion of the surface of the three-dimensional object by a flat face; b) fixing the inclination of the flat face of the step a) to a predetermined inclination; and c) supplying ink to the surface of the three-dimensional object while performing two-dimensional scanning in a plane parallel to the flat face of step b).
This method permits a high-speed printing operation as compared with that of controlling a printing operation in accordance with the shape of a three-dimensional object.
According to another aspect of the present invention, the method comprises the steps of: a) locating the three-dimensional object opposite an ejection head with a plurality of nozzles for ejecting ink; b) causing the ejection head to scan the surface of the three-dimensional object; and c) enabling predetermined nozzles and disabling the other nozzles out of the plurality of nozzles in accordance with a shape of the surface of the three-dimensional object located opposite the ejection head, thereby to eject ink from the enabled nozzles during the scanning.
This method permits proper printing on a three-dimensional printing object without image degradation.
According to still another aspect of the present invention, the method comprises the steps of: placing the three-dimensional object on a table which is rotatable about an axis perpendicular to a placing surface of the table; and rotating the table with an ejection head with a plurality of nozzles for ejecting ink being in a predetermined position in three-dimensional space, and ejecting ink from the ejection head in response to rotation of the table so that ink is supplied to the three-dimensional object with a predetermined width in a direction of the axis.
This method permits proper and high-speed printing on a three-dimensional printing object without image degradation.
Therefore, an object of the present invention is to perform proper printing on a three-dimensional printing object without image degradation by the use of a multinozzle ejection head.
Another object of the present invention is to facilitate control of the inclination and position of the ejection section for ejecting ink relative to the surface of a three-dimensional object, thereby achieving a high-speed printing operation.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.